Systems which allow an analysis without handling liquid reagents are primarily used in the fields of medicine and environmental analysis. They are referred to as dry tests. With these systems, the user can carry out analytical tests for individual parameters without having the necessary scientific background in chemistry or biochemistry. If all instructions are carried out properly, the measurements will be exact. Such systems can, hence, be used by untrained personnel, and are consequently of particular significance in the medical field when Used by patients.
In the last years, instruments for monitoring blood glucose levels by the patients have gained more and more importance. The use of instruments which can be carried along at any time makes the patient largely independent of the treating physician and, hence, increases the patient's quality of life. The option of simple and fast measurement improves drug administration, e.g. stabilization of the blood glucose level by administering insulin or sugar corresponding to the organism's requirement. Even the patient's way of living can thus be adjusted to the actual needs of the body. In the future, portable patient-operated instruments will also be employed for the determination of other blood components. In addition to endogenous substances, this includes the monitoring of drug concentrations in the blood. Such monitoring gains particular importance if the pharmacological spectrum of a therapeutic agent is narrow, as it is the case with digitalis steroids or lithium, for example.
In currently known embodiments of instruments for measuring the components of body fluids, instrument and test reagents are separated. The test reagents are available, for example, in the form of test strips onto which the body fluid is applied. The test strip is then inserted into the instrument for measurement. The storage stability of many reagents is drastically reduced by moisture. A known possibility of ensuring the storage stability of test elements over a longer period of time is to seal them in metal foil. This is usually done with urine test strips, for example. Another possibility of storing moisture-sensitive reagents is to store a great number of test elements in containers, i.e. usually vials which are made of a material that is impermeable to humidity. The test elements can then be individually removed from these containers. When the containers are opened, however, moisture can enter together with the ambient air. In order to ensure a certain storage stability of the remaining test elements, a drying agent to absorb any moisture that may have entered is provided inside the container. The user must, hence, carry a separate supply of test elements in addition to the instrument.
A procedure for analyzing a sample liquid known in prior art, for example for the determination of glucose in blood, comprises the following operating steps:
Manual removal of a test strip from a separate storage container PA1 Application of the sample liquid PA1 Inserting a test element into the instrument PA1 Carrying out the measurement PA1 Reading off the measurement value PA1 Discarding the used test element. PA1 a) they are provided with a tip or an edge which facilitates piercing of the sealing when the element is removed from its sealing, and/or PA1 b) they are provided with a notch which serves as a contact point for a mechanical unit, or PA1 c) they are provided with guiding elements which prevent a movement perpendicular to the main direction of movement during transportation parallel to the opposing sites in one of the rails receiving the guarding elements. PA1 Removing a test element from its sealing by means of a device PA1 Transporting the test element to the site of sample application PA1 Applying a sample onto the test element PA1 Reading off the measurement.
The above-mentioned precautions against humidity must already be taken when removing a test element from a separate container. Further, the test strip may be contaminated by did adhering to the hands which could ultimately lead to false test results. Another source of contamination of the test strip is by accidentally dropping it. The following steps of sample application and insertion into the instrument are switched in some prior art instruments. In these cases, sample application is carried out while the test element is already in the instrument. This facilitates, for example, application of a blood droplet from the tip of a finger, which has been pricked with a lancet, as the test element is fixed in its position by the instrument.
In known analysis systems where individual test elements are employed, the user manually moves such an element to the site of measurement. In order to avoid errors due to incorrect positioning, the instrument must be given a corresponding structural design. Test elements in the form of a strip, for example, are inserted into a given guide element until contact is made with an abutment.
Analysis can be accomplished by a way of detectable signals whose strength depends on the concentration of the parameter to be determined in the sample. The expert is familiar with detectable signals that are suitable for such analyses, e.g. optical, electrical, or magnetic signals.
In instruments for use with test elements, the measurement is usually carried out by means of reflectance photometry. Less used instruments are those which employ transparent test elements where the detection is quantified in terms of the transmission. The measurements are evaluated with electronic and usually also digital means.
Analysis instruments containing a multitude of test strips have so far been limited to laboratories or larger physicians' offices as these places achieve a high throughput of individual tests rendering additional precautions against humidity and the influence of light superfluous. Patent application EP-A-0513618, for example, describes a radial arrangement of test elements. The test elements are removed from the arrangement by means of a mechanical device and the sample liquid is applied by means of a pipette. As opposed to the present invention, the test elements are not sealed inside the instrument. This arrangement was, therefore, designed to use all test elements within a short time, usually minutes or hours.